Process for preparing hydrocarbon mixture exhibiting unique branching structure

ABSTRACT

Provided herein is a unique process that prepares a saturated hydrocarbon mixture with well-controlled structural characteristics that address the performance requirements driven by the stricter environmental and fuel economy regulations for automotive engine oils. The process allows for the branching characteristics of the hydrocarbon molecules to be controlled so as to consistently provide a composition that has a surprising CCS viscosity at −35° C. (ASTM D5329) and Noack volatility (ASTM D5800) relationship. The process comprises providing a specific olefinic feedstock, oligomerizing in the presence of a BF 3  catalyst, and hydroisomerizing in the presence of a noble-metal impregnated, 10-member ring zeolite catalyst.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/398,683 filed Apr. 30, 2019, which claims priority to U.S.Provisional Application No. 62/733,698 filed Sep. 20, 2018, the completedisclosures of which are incorporated herein by reference in theirentireties.

FIELD OF THE INVENTION

A process has been developed for preparing high performance hydrocarbonmixtures which possess unique compositional characteristics and whichdemonstrate superior low temperature and volatility properties.

BACKGROUND OF THE INVENTION

Base stocks are commonly used to produce various lubricants, includinglubricating oils for automobiles, industrial oils, turbine oils,greases, metal working fluids, etc. They are also used as process oils,white oils, and heat transfer fluids. Finished lubricants generallyconsist of two components, base oils and additives. Base oil, whichcould be one or a mixture of base stocks, is the major constituent inthese finished lubricants and contributes significantly to theirperformances, such as viscosity and viscosity index, volatility,stability, and low temperature performance. In general, a few basestocks are used to manufacture a wide variety of finished lubricants byvarying the mixtures of individual base stocks and individual additives.

The American Petroleum Institute (API) categorizes base stocks into fivegroups based on their saturated hydrocarbon content, sulfur level, andviscosity index (Table 1 below). Group I, II, and III base stocks aremostly derived from crude oil via extensive processing, such as solventrefining for Group I, and hydroprocessing for Group II and Group III.Certain Group III base stocks can also be produced from synthetichydrocarbon liquids via a Gas-to-Liquids process (GTL), and are obtainedfrom natural gas, coal or other fossil resources. Group IV base stocks,the polyalphaolefins (PAO), are produced by oligomerization of alphaolefins, such as 1-decene. Group V base stocks include everything thatdoes not belong to Groups I-IV, such as naphthenic base stocks,polyalkylene glycols (PAG), and esters. Most of the feedstocks forlarge-scale base stock manufacturing are non-renewable.

TABLE 1 API Base Oil Classification (API 1509 Appendix E) ViscosityIndex Saturates by API (ASTM ASTM Sulphur, Group D2270) D2007 %Description I 80-119  <90% >.03% Conventional (solvent refining) II80-119 ≥90% ≤.03% Hydroprocessing III ≥120 ≥90% ≤.03% SevereHydroprocessing IV PolyAlphaOlefins (PAO) V All other base stocks notincluded above e.g. esters

Automotive engine oils are by far the largest market for base stocks.The automotive industry has been placing more stringent performancespecifications on engine oils due to requirements for lower emissions,longer drain intervals, and better fuel economy. Specifically,automotive OEMs (original equipment manufacturer) have been pushing forthe adoption of lower viscosity engine oils such as 0W-20 to 0W-8, tolower friction losses and achieve fuel economy improvement. Group II'susage in 0W-xx engine oils is highly limited because formulationsblended with these base stocks cannot meet the performancespecifications for 0W-xx engine oils, leading to increased demands forGroup III and Group IV base stocks.

Group III base stocks are mostly manufactured from vacuum gas oils(VGOs) through hydrocracking and catalytic dewaxing (e.g.hydroisomerization). Group III base stocks can also be manufactured bycatalytic dewaxing of slack waxes originating from solvent refining, orby catalytic dewaxing of waxes originating from Fischer-Tropschsynthesis from natural gas or coal based raw materials also known as Gasto Liquids base oils (GTL).

Manufacturing processes of Group III base stocks from VGOs are discussedin U.S. Pat. Nos. 5,993,644 and 6,974,535. The boiling pointdistributions of Group III base stocks are typically higher than PAOs ofthe same viscosity, causing them to have higher volatility than PAOs.Additionally, Group III base stocks typically have higher cold crankviscosity (i.e., dynamic viscosity measured according to ASTM D5293,CCS) than Group IV base stocks at equivalent viscosities.

GTL base stock processing is described in U.S. Pat. Nos. 6,420,618 and7,282,134, as well as U.S. Patent Application Publication 2008/0156697.For example, the latter publication describes a process for preparingbase stocks from a Fischer-Tropsch synthesis product, the fractions ofwhich with proper boiling ranges are subjected to hydroisomerization toproduce GTL base stocks.

Structures and properties of GTL base stocks are described, for example,in U.S. Pat. Nos. 6,090,989 and 7,083,713, as well as U.S. PatentApplication Publication 2005/0077208. In U.S. Patent ApplicationPublication 2005/0077208, lubricant base stocks with optimized branchingare described, which have alkyl branches concentrated toward the centerof the molecules to improve the base stocks' cold flow properties.Nevertheless, pour points for GTL base stocks are typically worse thanPAO or other synthetic hydrocarbon base stocks.

A further concern with GTL base stocks is the severely limitedcommercial supply, a result of the prohibitively large capitalrequirements for a new GTL manufacturing facility. Access to low costnatural gas is also required to profitably produce GTL base stocks.Additionally, as GTL base stocks are typically distilled from anisomerized oil with a wide boiling point distribution, the processresults in a relatively low yield to the base stock with a desiredviscosity when compared to that of a typical PAO process. Due to thesemonetary and yield constraints there is currently only a singlemanufacturing plant of group III+ GTL base stocks, exposing formulationsthat use GTL to supply chain and price fluctuation risks.

Polyalphaolefins (PAOs), or Group IV base oils, are produced bypolymerizing alphaolefins in the presence of a Friedel Crafts catalystsuch as AlCl₃, BF₃, or BF₃ complexes. For example, 1-octene, 1-decene,and 1-dodecene have been used to manufacture PAOs that have a wide rangeof viscosities, varying from low molecular weight and low viscosity ofabout 2 cSt at 100° C., to high molecular weight, viscous materials withviscosities exceeding 100 cSt at 100° C. The polymerization reaction istypically conducted in the absence of hydrogen; the lubricant rangeproducts are thereafter polished or hydrogenated to reduce the residualunsaturation. Processes to produce PAO based lubricants are disclosed,for example, in U.S. Pat. Nos. 3,382,291; 4,172,855; 3,742,082;3,780,128; 3,149,178; 4,956,122; 5,082,986; 7,456,329; 7,544,850; andU.S. Patent Application Publication 2014/0323665.

To meet the increasingly stringent performance requirements ofautomotive engine oils and other modern lubricants, low-viscositypolyalphaolefin base stocks derived from 1-decene have been particularlyfavored. They are used either alone or in blends with other mineral basestocks in the lubricant formulations. However, the 1-decene basedpolyalphaolefins can be prohibitively expensive due to the limitedsupply of 1-decene. Attempts to overcome the availability constraint of1-decene have led to the production of PAOs from C8 through C12 mixedalpha-olefin feeds, lowering the amount of 1-decene that is needed toimpart the properties. However, they still do not completely remove therequirement for providing 1-decene as the predominate olefin feedstockdue to performance requirements.

Alternatively, PAOs made with linear alphaolefins in the C14-C20 rangehave unacceptably high pour points, which are unsuitable for use in avariety of lubricants, including 0W-xx engine oils.

Therefore, there remains a need for cost-effective manufacturingprocesses that yield a base stock composition having superior propertiesfor use in most-stringent automotive and other lubricant applications,with such properties including one or more of viscosity, Noackvolatility, and low temperature fluidity.

In addition to the technical demands for the automotive industry,environmental awareness and regulations are driving manufacturers to userenewable feedstocks and raw materials in the production of base stocksand lubricants. Processes which can provide the desired base stockswhile also exploiting the use of renewable feedstocks would be greatlywelcome.

SUMMARY OF THE INVENTION

The present invention relates to a unique process that prepares asaturated hydrocarbon mixture with well-controlled structuralcharacteristics that address the performance requirements driven by thestricter environmental and fuel economy regulations for automotiveengine oils. The process allows for the branching characteristics of thehydrocarbon molecules to be controlled so as to consistently provide acomposition that has a surprising CCS viscosity at −35° C. (ASTM D5329)and Noack volatility (ASTM D5800) relationship.

In one aspect, the present process comprises of providing an olefinicfeedstock of C14 to C20 olefins having less than 40 wt % branchedolefins and greater than 50% alpha olefins. The feedstock isoligomerized in the presence of a boron trifluoride catalyst at areaction temperature in the range of 20-60° C. Oligomerized product isthen hydroisomerized in the presence of a noble-metal impregnated, 10member ring zeolite catalyst.

The resulting product is a saturated hydrocarbon mixture having greaterthan 80% of the molecules with an even carbon number according to FIMS.When the hydrocarbon mixture is analyzed by carbon NMR, it exhibits abranching characteristic of BP/BI≥−0.6037 (Internal alkyl branching permolecule)+2.0, and has on average at least 0.3 to 1.5 5+ methyl branchesper molecule.

In another aspect, the process further comprises recovering a productfrom the oligomerization and removing unreacted monomer from the productas an olefin before the hydroisomerization. The recovered product fromwhich the unreacted monomer has been removed is then separated into twoproduct fractions, with one fraction comprising greater than 95 wt %dimers having a maximum carbon number of 40, and a product fractioncomprising greater than 95% trimers and higher oligomerized compoundshaving a minimum carbon number of 42. The two fractions arehydroisomerized separately. In still another aspect, the dimer fractionseparated comprising greater than 95 wt % dimers, if hydrogenatedwithout hydroizomerization, has a branching proximity of 27 to 35.

Another aspect, provided is a process providing an olefinic feedstockcomprising less than 8 wt % branched monomeric olefins and greater than90 wt % monomeric alpha olefins, with the monomeric olefins having acarbon number in the range of from C14-C20. An oligomerization reactionis conducted with the olefinic feedstock at a temperature in the rangeof 20-60° C., in the presence of BF₃ and BuOH/BuAc co-catalyst, with areaction residence time of from 60-180 minutes, in a semi-batch orcontinuous stirred tank reactor. A product is recovered from theoligomerization reaction and unreacted olefin monomer is removed bydistillation. A bottom product is recovered from the distillation andthe product is hydroisomerized over a noble-metal impregnated,one-dimensional zeolite with a 10-member ring at a pressure in the rangeof 100-800 psig; a temperature in the range of from 290-350° C.; and ahydrogen flow rate of 500-3500 scf/bbl. Following hydroisomerization theproduct is distilled into two fractions. One fraction comprising ofapproximately greater than 95 wt % dimers and a second fractioncomprising of approximately greater than 95 wt % trimers and higheroligomers. In another aspect, the product recovered from theoligomerization has the unreacted monomer olefin removed bydistillation, and the bottoms are hydrogenated and then hydroisomerizedbefore the final production distillation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the relationship between BP/BI and Internal AlkylBranches per Molecule for various hydrocarbons, including low-viscosityPAO manufactured from 1-decene and 1-dodecene, GTL base oils, andhydroisomerized hexadecene oligomers. The straight line in the plotdepicts the equation of BP/BI=−0.6037 (Internal alkyl branching permolecule)+2.0.

FIG. 2 illustrates the relationship between BP/BI and 5+ Methyl Branchesper Molecule for various hydrocarbons, including low-viscosity PAOmanufactured from 1-decene and 1-dodecene, GTL base oils, andhydroisomerized hexadecene oligomers. It demonstrates that the 5+ MethylBranches per Molecules for the hydrocarbon mixtures disclosed in thispatent fall in a unique range of 0.3-1.5.

FIG. 3 illustrates the relationship between NOACK volatility and CCS at−35° C. for various hydrocarbons, including low-viscosity PAOmanufactured from 1-decene and 1-dodecene, GTL base oils, Group III baseoils, and hydroisomerized hexadecene oligomers. The solid line anddotted line depicts the upper limit and lower limit of the Noack vs. CCSat −35° C. exhibited by the present unique hydrocarbon mixture, whichare NOACK=2,750 (CCS at −35° C.)^((−0.8))+2 and NOACK=2,750 (CCS at −35°C.)^((−0.8))−2, respectively.

FIG. 4 depicts one embodiment of the present process where a dimerproduct and trimer product are separated after hydroisomerization. Theoligomers are also hydrogenated prior to hydroisomerization.

FIG. 5 depicts another embodiment of the present process where a dimerproduct and trimer product are separated after hydroisomerization. Theoligomers are not saturated prior to the hydroisomerization step.

FIG. 6. depicts an embodiment of the present process where a dimerproduct and a timer+ product are saturated and separated prior tohydroisomerization. Each product is then hydroisomerized separately.

FIG. 7 depicts a variation of the process in FIG. 6, where the oligomersare not hydrogenated prior to separation and hydroisomerization.

DETAILED DESCRIPTION

Disclosed herein is a process for preparing a saturated hydrocarbonmixture having a unique branching structure as characterized by NMR thatmakes it suitable to be used as a high-quality synthetic base stock. Theprocess comprises oligomerizing C14 to C20 olefin to form an oligomerproduct consisting of unreacted monomer, dimers (C28-C40), and trimersand higher oligomers (≥C42). The unreacted monomers can be distilled offfor possible re-use in a subsequent oligomerization. The remainingoligomers are then hydroisomerized to achieve the final hydrocarbonmixture having unique branching structures.

To be specific, the hydrocarbon mixture comprises greater than 80% ofthe molecules with an even carbon number according to FIMS. Thebranching characteristics of the hydrocarbon mixture by NMR indicates aBP/BI in the range ≥−0.6037 (Internal alkyl branching per molecule)+2.0.Moreover, on average, at least 0.3 to 1.5 of the internal methylbranches are located more than four carbons away from the end carbon. Asaturated hydrocarbon with this unique branching structure exhibits asurprising cold crank simulated viscosity (CCS) vs. Noack volatilityrelationship that is beneficial for blending low-viscosity automotiveengine oils.

Provided herein are processes or methods to make hydrocarbon mixtureshaving unique branching structures with associated beneficialproperties. The hydrocarbon mixtures can be synthesized via olefinoligomerization to achieve the desired carbon chain length, followed byhydroisomerization to improve their cold-flow properties, such as pourpoint and CCS, etc.

In one embodiment, olefins with 14-20 carbons in length are oligomerizedin the presence of a boron trifluoride acid catalyst to form an oligomermixture. The olefins can be sourced from natural occurring molecules,such as crude oil or gas based olefins, or from ethylenepolymerizations. In some variations, about 100% of the carbon atoms inthe olefin feedstocks described herein may originate from renewablecarbon sources. For example, an alpha-olefin monomer may be produced byoligomerization of ethylene derived from dehydration of ethanol producedfrom a renewable carbon source. In some variations, an alpha-olefinmonomer may be produced by dehydration of a primary alcohol other thanethanol that is produced from a renewable carbon source. Said renewablealcohols can be dehydrated into olefins, using gamma alumina or sulfuricacid. In some embodiments, modified or partially hydrogenated terpenefeedstocks derived from renewable resources are coupled with one or moreolefins that are derived from renewable resources.

The mixture of C14-C20 olefins to create an olefinic feedstock can beselected from the group consisting of 1-tetradecene, 1-pentadecene,1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene (and/or optionallybranched structural isomers of these olefins) and/or internal olefinsderived from linear internal or branched internal pentadecenes,hexadecenes, heptadecenes, octadecenes, and eicosene. In one embodiment,the olefin monomers of the feed mixture may be selected from the groupconsisting of unsaturated, linear alpha-olefins, unsaturated, linearinternal olefins, branched alpha olefins, branched internal olefins, andcombinations thereof. In yet another embodiment, the olefin monomers ofthe feed mixture may comprise a mixture of linear alpha olefins and/orlinear internal olefins. According to certain embodiments, the longerlinear paraffin branches produced from C14-C20 olefins increases the VIand reduce the CCS of the oligomers, while the pour point of theoligomers can be reduced by the introduction of branching throughisomerization of the dimer.

In one embodiment of the invention the olefinic feedstock consists ofolefins from 14 to 20 carbons in length comprising of less than 40 wt %branched content. In yet another embodiment of the invention theolefinic feedstock comprises of olefins with less than 30% branchedcontent. In yet another embodiment the olefinic feedstock comprises ofolefins with less than 20% branched content. In yet another embodimentthe olefinic feedstock comprises of olefins with less than 8% branchedcontent. In a preferred embodiment the olefinic feedstock comprises ofless than 3 wt % branched content. Branching in an olefin will decreasethe linearity of the resulting oligomer from an oligomerizationreaction. The branching imparted to the oligomer through branchedolefins will decreased viscosity index without sufficiently reducing thecold flow properties such as pour point and CCS.

In one embodiment of the invention the olefinic feedstock contains atleast 50% alpha olefins. In yet another embodiment the olefinicfeedstock contains at least 70% alpha olefins. In yet another embodimentthe olefinic feedstock contains at least 80% alpha olefins. In apreferred embodiment the olefinic feedstock contains at least 90% alphaolefins. Oligomerization of an olefinic feedstock without enough alphaolefin content will reduce the linearity of the oligomer. Depending onthe double bond position on the carbon chain of the monomeric feedstock,the branching proximity of the oligomer could be reduced compared to anoligomer made from alpha olefins of an equivalent chain length. Whilethe presence of long chain branching will reduce the pour point, it willalso lead to the undesired reduction of viscosity index and increase ofCCS.

In addition to the olefinic feedstock, the oligomerization conditionshave strong impacts on the structure and properties of the oligomerproducts. In one embodiment, an olefin monomer between C14 to C20 isoligomerized in the presence of BF₃ and/or BF₃ promoted with a mixtureof an alcohol and/or an ester, such as a linear alcohol and an alkylacetate ester, in a continuously stirred tank reactor (CSTR) with anaverage residence time of 60 to 400 minutes. In another embodiment, theC14 to C20 olefin monomers are oligomerized in the presence of BF₃and/or promoted BF₃ in a CSTR with an average residence time of 90 to300 minutes. In yet another embodiment, the C14 to C20 the olefinmonomers are oligomerized in the presence of BF₃ and/or promoted BF₃ ina CSTR with an average residence time of 120 to 240 minutes. Thetemperature of the oligomerization reaction may be in a range of from10° C. to 90° C. However, in one preferred embodiment, the temperatureis maintained in the range of from 15 to 75° C., and most preferably 20°C. to 60° C., for the duration of the reaction. It was discovered thatthe reaction temperature has a strong impact on the degree ofisomerization taking place during the oligomerization process. Highertemperature oligomerization would increase isomerization and lead to amore branched oligomer product, which is evidenced by the reduction ofthe branching proximity for the saturated dimer intermediate. Where thesaturated dimer intermediate is defined as oligomerization dimer, it hasbeen isolated by distillation to <5% trimer or greater oligomers andhydrogenated without isomerization. Such branched dimers do not have thedesired structure, such as 5+ methyl branching per molecule, nor do theypose the required linearity to be used as an ideal hydroisomerizationfeed, i.e., an oligomers created at too high of a temperature wouldyield undesirable physical properties such as lower viscosity index andhigher Noack volatility after hydroisomerization, in comparison to thoseobtained from hydroisomerization of a more linear dimer fraction to thesame pour point. Direct effects of oligomerization reaction temperaturesare illustrated in examples 14-16.

Proper control of the oligomerization reaction temperature and residencetime within a CSTR is needed to ensure the dimer portion (C28-C40) ofthe oligomerization product has branching proximity (BP) between 25 to35, preferably between 27 to 35, more preferably between 27-33, and mostpreferably between 28-32, if the dimer portion were to be saturated to aBr index of less than 100 mg Bra/100 g (ASTM D2710). A branchingproximity which is too low prior to hydroisomerization will lead toisomerized hydrocarbon mixtures that fall under the solid line in FIG. 1and will result in a less desirable higher CCS viscosity at −35° C.value for a given Noack volatility to fit within the range shown in FIG.3. Conversely, a branching proximity which is too high will requiregreater isomerization to reach an acceptable pour point, which willincrease the Noack volatility and the CCS at −35° C. simultaneously.

In one embodiment, the unsaturated oligomer product is distilled toremove the unreacted monomer as an olefin. For example, the unreactedmonomer may be separated from the oligomer product, such as viadistillation, and can be recycled back into the olefin feed stock foroligomerization thereof.

The oligomer product is then hydroisomerized to provide the additionalbranches required to achieve the ideal branching characteristics. In oneembodiment, the whole oligomer product, including both the dimers(C28-C40) and heavier oligomers (≥C42), are hydroisomerized prior toseparation by distillation. The hydroisomerized product is thenseparated into the final hydrocarbon products by distillation. Inanother embodiment, the dimers and heavier oligomers are fractionatedand hydroisomerized separately.

Hydroisomerization catalysts useful in the present invention usuallycomprises a shape-selective molecular sieve, a metal or metal mixturethat is catalytically active for hydrogenation, and a refractory oxidesupport. The presence of a hydrogenation component leads to improvementin product stability. Typical catalytically active hydrogenation metalsinclude chromium, molybdenum, nickel, vanadium, cobalt, tungsten, zinc,platinum, and palladium. Platinum and palladium are especiallypreferred, with platinum mostly preferred. If platinum and/or palladiumis used, the metal content is typically in the range of 0.1 to 5 weightpercent of the total catalyst, usually from 0.1 to 2 weight percent, andnot to exceed 10 weight percent. Hydroisomerization catalysts arediscussed, for example, in U.S. Pat. Nos. 7,390,763 and 9,616,419, aswell as U.S. Patent Application Publications 2011/0192766 and2017/0183583.

The conditions for hydroisomerization are tailored to achieve anisomerized hydrocarbon mixture with specific branching properties, asdescribed above, and thus will depend on the characteristics of feedused. The reaction temperature is generally between about 200° C. and400° C., preferably between 260° C. to 370° C., most preferably between288° C. to 345° C., at a liquid hourly space velocity (LHSV) generallybetween about 0.5 hr⁻¹ and about 5 hr⁻¹. The pressure is typically fromabout 15 psig to about 2500 psig, preferably from about 50 psig to about2000 psig, more preferably from about 100 psig to about 1500 psig, mostpreferably 100 to 800 psig. Low pressure provides enhanced isomerizationselectivity, which results in more isomerization and less cracking ofthe feed, thus leading to an increased yield of hydrocarbon mixture inthe base stock boiling range.

Hydrogen is present in the reaction zone during the hydroisomerizationprocess, typically in a hydrogen to feed ratio from about 0.1 to 10MSCF/bbl (thousand standard cubic feet per barrel), preferably fromabout 0.3 to about 5 MSCF/bbl. Hydrogen may be separated from theproduct and recycled to the reaction zone.

In one embodiment, an additional step of hydrogenation is added beforehydroisomerization to protect the downstream hydroisomerizationcatalyst. In another embodiment, an additional step of hydrogenation orhydrofinishing is added after the hydroisomerization to further improvethe saturation and stability of the hydrocarbon mixture.

The hydroisomerized hydrocarbon mixtures are comprised of dimers havingcarbon numbers in the range of C28-C40, and a mixture of trimers+ havingcarbon numbers of C42 and greater. Each of the hydrocarbon mixtures willexhibit a BP/BI in the range of ≥−0.6037 (internal alkyl branching)±2.0per molecule, and, on average, from 0.3 to 1.5 methyl branches on thefifth or greater position per molecule. Importantly, at least 80% of themolecules in each composition also have an even carbon number asdetermined by FIMS. In another embodiment, each of the hydrocarboncompositions will also exhibit a Noack and CCS at −35° C. relationshipsuch that the Noack is between 2750 (CCS at −35° C.)^((−0.8))±2. Thesecharacteristics allow for the formulation of low-viscosity engine oilsas well as many other high-performance lubricant products.

In one embodiment, C16 olefins are used as the feed for theoligomerization reaction. When using C16 olefins as the feed, thehydroisomerized dimer product generally exhibits a KV100 of 4.3 cSt with<8% Noack loss and a CCS at −35° C. of approximately 1,700 cP. Theextremely low Noack volatility is due to the high initial boiling pointand narrow boiling point distribution when compared other 3.9 to 4.4 cStsynthetic base stocks. This makes the dimer product ideal for use in lowviscosity engine oils with strict volatility requirements. The excellentCCS and pour point characteristics are due to the branchingcharacteristics discussed above. In one embodiment, the dimer producthas a pour point of ≤−40° C. This is required to pass critical engineoil formulation requirements for 0W formulations, including Mini-RotaryViscosity (ASTM D4684) and Scanning Brookfield Viscosity (ASTM D2983)specifications.

Different embodiments of the present process are depicted in blockdiagrams FIGS. 4-7.

FIG. 4 depicts a preferred embodiment including the selection of anolefin feed using a mixture or single olefin of 14 to 20 carbons inlength (1). Oligomerizing said olefins in the presence of BF₃ and apromoter (13) in either semi-batch or CSTR mode (2). Subsequently,removing the unreacted monomer olefin by distillation (3). Optionally,the unreacted monomer can be recycled back into the oligomerizationreactor (12). The dimer and higher oligomers are then simultaneouslysaturated (4) and hydroisomerized (5). Cracked light products (11)formed during hydroisomerization are removed by distillation (6). Theremaining oligomers are then separated via distillation (7) into thefinal dimer (9) and trimer+ products (10).

FIG. 5 depicts an embodiment involving the selection of an olefin feedusing a mixture or single olefin of 14 to 20 carbons in length (14).Oligomerizing said olefins in the presence of BF₃ and a promoter (24) ineither semi-batch or CSTR mode (15). Subsequently, removing theunreacted monomer by distillation (16). Optionally, the unreacted olefinmonomer can be recycled back into the oligomerization reactor (23). Thedimer and higher oligomers are then hydroisomerized (17). Fullsaturation of the isomerized oligomers is achieved during thehydroisomerization process (17). Cracked light products (22) formedduring hydroisomerization are removed (18). The remaining oligomers arethen separated via distillation (19) into the final dimer (20) andtrimer+ products (21).

FIG. 6 depicts a variation on the process where the oligomerizationproduct is saturated (28) and distilled (29) prior to thehydroisomerization. The non-isomerized hydrogenated dimers (30) have abranching proximity between 27-35. The non-isomerized dimer (30) andtrimer+(35) products are then hydroisomerized (31, 36) separately andthe resulting cracked light streams (34, 39) are removed viadistillation (32, 37) to yield the final dimer (33) and trimer+(38)products.

FIG. 7 depicts a variation on the process where the oligomerdistillation (45) to separate the non-isomerized dimers from the trimer+oligomers (46, 51), is done prior to hydroisomerization. Full saturationof both the dimer and trimer+ fraction is achieved during thehydroisomerization process (47, 52). The cracked lights (50, 55) arethen removed from the hydroisomerized dimers and trimers by distillation(48, 53) to yield the final dimer (49) and trimer+(54) products.

As noted, the resulting hydrocarbon mixture obtained from the presentprocess has outstanding properties including extremely low volatility,good low-temperature properties, etc., which are important performanceattributes of high-quality base stocks. To be specific, the mixturecomprises greater than 80% of the molecules with an even carbon numberaccording to FINIS. The branching characteristics of the hydrocarbonmixture by NMR indicates a BP/BI in the range ≥−0.6037 (Internal alkylbranching per molecule)+2.0. Moreover, on average, at least 0.3 to 1.5of the internal methyl branches are located more than four carbons awayfrom the end carbon. These characteristics are illustrated in FIGS. 1-3of the drawings. A saturated hydrocarbon with this unique branchingstructure exhibits a surprising cold crank simulated viscosity (CCS) vs.Noack volatility relationship (FIG. 3) that is beneficial for blendinglow-viscosity automotive engine oils. The following definitions areoffered to better understand the uniqueness of the hydrocarbon mixtureproduct achieved by the present process.

Definitions of Hydrocarbon Properties

The following properties are used in describing the novel saturatedhydrocarbon mixtures:

Viscosity is the physical property that measures the fluidity of thebase stock. Viscosity is a strong function of temperature. Two commonlyused viscosity measurements are dynamic viscosity and kinematicviscosity. Dynamic viscosity measures the fluid's internal resistance toflow. Cold cranking simulator (CCS) viscosity at −35° C. for engine oilis an example of dynamic viscosity measurements. The SI unit of dynamicviscosity is Pa·s. The traditional unit used is centipoise (cP), whichis equal to 0.001 Pa·s (or 1 m Pa·s). The industry is slowly moving toSI units. Kinematic viscosity is the ratio of dynamic viscosity todensity. The SI unit of kinematic viscosity is mm²/s. The other commonlyused units in industry are centistokes (cSt) at 40° C. (KV40) and 100°C. (KV100) and Saybolt Universal Second (SUS) at 100° F. and 210° F.Conveniently, 1 mm²/s equals 1 cSt. ASTM D5293 and D445 are therespective methods for CCS and kinematic viscosity measurements.

Viscosity Index (VI) is an empirical number used to measure the changein the base stock's kinematic viscosity as a function of temperature.The higher the VI, the less relative change is in viscosity withtemperature. High VI base stocks are desired for most of the lubricantapplications, especially in multigrade automotive engine oils and otherautomotive lubricants subject to large operating temperature variations.ASTM D2270 is a commonly accepted method to determine VI.

Pour Point is the lowest temperature at which movement of the testspecimen is observed. It is one of the most important properties forbase stocks as most lubricants are designed to operate in the liquidphase. Low pour point is usually desirable, especially in cold weatherlubrication. ASTM D97 is the standard manual method to measure pourpoint. It is being gradually replaced by automatic methods, such as ASTMD5950 and ASTM D6749. ASTM D5950 with 1° C. testing interval is used forpour point measurement for the examples in this patent.

Volatility is a measurement of oil loss from evaporation at an elevatedtemperature. It has become a very important specification due toemission and operating life concerns, especially for lighter grade basestocks. Volatility is dependent on the oil's molecular composition,especially at the front end of the boiling point curve. Noack (ASTMD5800) is a commonly accepted method to measure volatility forautomotive lubricants. The Noack test method itself simulatesevaporative loss in high temperature service, such as an operatinginternal combustion engine.

Boiling point distribution is the boiling point range that is defined bythe True Boiling Points (TBP) at which 5% and 95% materials evaporates.It is measured by ASTM D2887 herein.

NMR Branching Analysis:

All branching parameters are to be measured on hydrocarbons with <1000Br index mg Br/100 g. Branching parameters measured by NMR spectroscopyfor the hydrocarbon characterization include:

Branching Index (BI): the percentage of methyl hydrogens appearing inthe chemical shift range of 0.5 to 1.05 ppm among all hydrogensappearing in the 1H NMR chemical range 0.5 to 2.1 ppm in anisoparaffinic hydrocarbon.

Branching Proximity (BP): the percentage of recurring methylene carbonswhich are four or more number of carbon atoms removed from an end groupor branch appearing at ¹³C NMR chemical shift 29.8 ppm.

Internal Alkyl Carbons: is the number of methyl, ethyl, or propylcarbons which are three or more carbons removed from end methyl carbons,that includes 3-methyl, 4-methyl, 5+ methyl, adjacent methyl, internalethyl, n-propyl and unknown methyl appearing between ¹³C NMR chemicalshift 0.5 ppm and 22.0 ppm, except end methyl carbons appearing at 13.8ppm.

5+ Methyl Carbons: is the number of methyl carbons attached to a methinecarbon which is more than four carbons away from an end carbon appearingat 13C NMR chemical shift 19.6 ppm in an average isoparaffinic molecule.

The feedstock can be defined in terms of alpha, branched and internalolefins.

Catalyst definition: Butanol and Butyl Acetate are to be described asn-Butanol and Butyl Acetate as n-Butyl-Acetate.

Alpha-olefin: unsaturated hydrocarbon with a chemical formula C_(x)H2x,distinguished by having a double bond at the primary or alpha positionand having a linear hydrocarbon chain.

Branched olefin: an olefin in which the carbon structure has one or moretertiary carbons.

Internal olefin: an olefin in which the unsaturation is not in aterminal position.

The NMR spectra were acquired using Bruker AVANCE 500 spectrometer usinga 5 mm BBI probe. Each sample was mixed 1:1 (wt:wt) with CDCl₃. The ¹HNMR was recorded at 500.11 MHz and using a 9.0 μs (30°) pulse applied at4 s intervals with 64 scans co-added for each spectrum. The ¹³C NMR wasrecorded at 125.75 MHz using a 7.0 μs pulse and with inverse gateddecoupling, applied at 6 sec intervals with 4096 scans co-added for eachspectrum. A small amount of 0.1 M Cr(acac)₃ was added as a relaxationagent and TMS was used as an internal standard.

The branching properties of the lubricant base stock samples of thepresent invention are determined according to the following six-stepprocess. Procedure is provided in detail in US 20050077208 A1, which isincorporated herein in its entirety. The following procedure is slightlymodified to characterize the current set of samples:

-   -   1) Identify the CH branch centers and the CH₃ branch termination        points using the DEPT Pulse sequence (Doddrell, D. T.; D. T.        Pegg; M. R. Bendall, Journal of Magnetic Resonance 1982, 48,        323ff.).    -   2) Verify the absence of carbons initiating multiple branches        (quaternary carbons) using the APT pulse sequence (Patt, S.        L.; J. N. Shoolery, Journal of Magnetic Resonance 1982, 46,        535ff.).    -   3) Assign the various branch carbon resonances to specific        branch positions and lengths using tabulated and calculated        values (Lindeman, L. P., Journal of Qualitative Analytical        Chemistry 43, 1971 1245ff; Netzel, D. A., et. al., Fuel, 60,        1981, 307ff.).

Branch NMR Chemical Shift (ppm)

TABLE 2 Describes ppm shift of alkyl branching by Carbon NMR Branch NMRChemical Shift (ppm) 2-methyl 22.5 3-methyl 19.1 or 11.4 4-methyl 14.05+ methyl 19.6 Internal ethyl 10.8 n-propyl 14.4 Adjacent methyl 16.7

-   -   4) Quantify the relative frequency of branch occurrence at        different carbon positions by comparing the integrated intensity        of its terminal methyl carbon to the intensity of a single        carbon (total integral/number of carbons per molecule in the        mixture). For example, number of 5+ methyl branches per molecule        is calculated from the signal intensity at a chemical shift of        19.6 ppm relative to intensity of a single carbon.    -   For the unique case of the 2-methyl branch, where both the        terminal and the branch methyl occur at the same resonance        position, the intensity was divided by two before doing the        frequency of branch occurrence calculation.    -   If the 4-methyl branch fraction is calculated and tabulated, its        contribution to the 5+ methyls must be subtracted to avoid        double counting.    -   Unknown methyl branches are calculated from contribution of        signals that appear between 5.0 ppm and 22.5 ppm, however not        including any branches reported in Table 2.    -   5) Calculate the Branching Index (BI) and Branching Proximity        (BP) using the calculations described in U.S. Pat. No.        6,090,989, which is incorporated by reference herein in its        entirety.    -   6) Calculate the total internal alkyl branches per molecule by        adding up the branches found in steps 3 and 4, except the        2-methyl branches. These branches would include 3-methyl,        4-methyl, 5+ methyl, internal ethyl, n-propyl, adjacent methyl        and unknown methyl.

FIMS Analysis: The hydrocarbon distribution of the current invention isdetermined by FIMS (field ionization mass spectroscopy). FIMS spectrawere obtained on a Waters GCT-TOF mass spectrometer. The samples wereintroduced via a solid probe, which was heated from about 40° C. to 500°C. at a rate of 50° C. per minute. The mass spectrometer was scannedfrom m/z 40 to m/z 1000 at a rate of 5 seconds per decade. The acquiredmass spectra were summed to generate one averaged spectrum whichprovides carbon number distribution of paraffins and cycloparaffinscontaining up to six rings.

Hydrocarbon Structure and Properties

The structure of the hydrocarbon mixtures disclosed herein arecharacterized by FIMS and NMR. FIMS analysis demonstrate that more than80% of the molecules in the hydrocarbon mixtures have an even carbonnumber.

The unique branching structure of the hydrocarbon mixtures disclosedherein are characterized by NMR parameters, such as BP, BI, internalalkyl branching, and 5+ methyls. BP/BI of the hydrocarbon mixtures arein the range of ≥−0.6037 (Internal alkyl branching per molecule)+2.0.The 5+ methyls of the hydrocarbon mixtures average from 0.3 to 1.5 permolecule.

The hydrocarbon mixture can be classified into two carbon ranges basedon the carbon number distribution, C28 to C40 carbons, and greater thanor equal to C42. Generally, about or greater than 95% of the moleculespresent in each hydrocarbon mixture have carbon numbers within thespecified range. Representative molecular structures for the C28 to C40range can be proposed based on the NMR and FIMS analysis. Withoutwishing to be bound to any one particular theory, it is believed thatthe structures made by oligomerization and hydroisomerization of olefinshas methyl, ethyl, butyl branches distributed throughout the structureand the branch index and branch proximity contribute to the surprisinglygood low temperature properties of the product. Exemplary structures inthe present hydrocarbon mixture are as follows:

The unique branching structure and narrow carbon distribution of thehydrocarbon mixtures makes them suitable to be used as high-qualitysynthetic base oils, especially for low-viscosity engine oilapplications. The hydrocarbon mixtures exhibit:

-   -   a KV100 in the range of 3.0-10.0 cSt;    -   a pour point in the range of −20 to −55° C.; and    -   a Noack and CCS at −35° C. relationship such that Noack is        between 2750 (CCS at −35° C.)^((−0.8))±2.

The Noack and CCS relationship for the hydrocarbon mixtures are shown inFIGS. 3 and 4. In each figure, the top line represents Noack=2750 (CCSat −35° C.)^((−0.8))+2 and the bottom graph line represents Noack=2750(CCS at −35° C.)^((−0.8))−2. More preferably the hydrocarbon mixtureshave a Noack and CCS at −35 C relationship such that the Noack isbetween Noack=2750 (CCS at −35° C.)^((−0.8))+0.5 and Noack=2750 (CCS at−35° C.)^((−0.8))−2. Hydrocarbon mixtures that are closer to the originin FIGS. 3 and 4 have been found more advantageous for low viscosityengine oils due to the low volatility and decreased viscosity at −35° C.

A hydrocarbon mixture in accordance with the present invention withcarbon numbers in the range of C28 to C40, and in another embodimentcarbon numbers in the range of from C28 to C36, or in another embodimentmolecules with a carbon number of C32, will generally exhibit thefollowing characteristics in addition to the characteristics of BP/BI,Internal alkyl branches per molecule, 5+ methyl branches per molecule,and Noack/CCS relationship described above:

-   -   a KV100 in the range of 3.0-6.0 cSt;    -   a VI in the range of 11 ln(BP/BI)+135 to 11 ln(BP/BI)+145; and    -   a pour point in the range of 33 ln(BP/BI)−45 to 33 ln(BP/BI)−35.

In one embodiment, the KV100 for the C28-C40 hydrocarbon mixture rangesfrom 3.2 to 5.5 cSt; in another embodiment the KV100 ranges from 4.0 to5.2 cSt; and from 4.1 to 4.5 cSt in another embodiment.

The VI for the C28-C40 hydrocarbon mixture ranges from 125 to 155 in oneembodiment and from 135 to 145 in another embodiment.

The Pour Point of the hydrocarbon mixture, in one embodiment ranges from25 to −55° C. and from 35 to −45° C. in another embodiment.

The boiling point range of the C28-C40 hydrocarbon mixture in oneembodiment is no greater than 125° C. (TBP at 95%−TBP at 5%) as measuredby ASTM D2887; no greater than 100° C. in another embodiment; no greaterthan 75° C. in one embodiment; no greater than 50° C. in anotherembodiment; and no greater than 30° C. in one embodiment. In thepreferred embodiments, those with a boiling point range no greater than50° C., and even more preferably no greater than 30° C., give asurprisingly low Noack Volatility (ASTM D5800) for a given KV100.

The C28-C40 hydrocarbon mixture in one embodiment has a BranchingProximity (BP) in the range of 14-30 with a Branching Index (BI) in therange of 15-25; and in another embodiment a BP in the range of 15-28 anda BI in the range of 16-24.

The Noack volatility (ASTM D5800) of the C28-C40 hydrocarbon mixture isless than 16 wt % in one embodiment; less than 12 wt % in oneembodiment; less than 10 wt % in one embodiment; less than 8 wt % in oneembodiment and less than 7 wt % in one embodiment. The C28-C40hydrocarbon mixture in one embodiment also has a CCS viscosity at −35°C. of less than 2700 cP; of less than 2000 cP in another embodiment; ofless than 1700 cP in one embodiment; and less than 1500 cP in oneembodiment.

The hydrocarbon mixture with the carbon number range of C42 and greaterwill generally exhibit the following characteristics, in addition to thecharacteristics of BP/BI, internal alkyl branches per molecule, 5+methyl branches per molecule, and Noack and CCS at −35° C. relationshipdescribed above:

-   -   a KV100 in the range of 6.0-10.0 cSt;    -   a VI in the range of 11 ln(BP/BI)+145 to 11 ln(BP/BI)+160; and    -   a Pour Point in the range of 33 ln(BP/BI)−40 to 33 ln(BP/BI)−25.

The hydrocarbon mixture comprising C42 carbons or greater, in oneembodiment has a KV100 in the range of 8.0 to 10.0 cSt, and in anotherembodiment from 8.5 to 9.5 cSt.

The VI of the hydrocarbon mixture having ≥42 carbons is 140-170 in oneembodiment; and, from 150-160 in another embodiment.

The pour point in one embodiment ranges from −15 to −50° C.; and, from−20 to −40° C. in another embodiment.

In one embodiment, the hydrocarbon mixture comprising ≥42 carbons has aBP in the range of 16-30 with a BI in the range of 15-25. In anotherembodiment, the hydrocarbon mixture has a BP in the range of 18-28 and aBI in the range of 17-23.

In general, both hydrocarbon mixtures disclosed above exhibit thefollowing characteristics:

-   -   at least 80% of the molecules have an even carbon number        according to FINIS;    -   a KV100 in the range of 3.0-10.0 cSt;    -   a pour point in the range of −20 to −55° C.;    -   a Noack and CCS @ −35° C. relationship such that Noack is        between 2750 (CCS @ −35° C.)^((−0.8))±2;    -   a BP/BI in the range of ≥−0.6037 (Internal alkyl branching)+2.0        per molecule; and    -   on average from 0.3 to 1.5 5+ methyl branches per molecule.        Lubricant Formulations

The hydrocarbon mixtures prepared by the present process can be used aslubricant base stocks to formulate final lubricant products comprisingadditives. In certain variations, a base stock prepared according to themethods described herein is blended with one or more additional basestocks, e.g., one or more commercially available PAOs, one or more Gasto Liquid (GTL) base stocks, one or more mineral base stocks, avegetable oil base stock, an algae-derived base stock, a second basestock as described herein, or any other type of renewable base stocks.Any effective amount of additional base stock may be added to reach ablended base oil having desired properties.

The present invention will be further illustrated by the followingexamples, which are not intended to be limiting.

EXAMPLES Examples 1-6 (C28-C40 Hydrocarbon Mixtures) Example 1

1-Hexadecene with less than 8% branched and internal olefins wasoligomerized under BF₃ with a co-catalyst composition of Butanol andButyl Acetate. The reaction was held at 20° C. during semi-continuousaddition of olefins and co-catalyst. The residence time was 90 minutes.The unreacted monomer was then distilled off, leaving behind less than0.1% monomer in the distillation bottoms. The dimer was then separatedfrom the trimer+ by distillation with less than 5% trimer remained inthe dimer cut.

The dimers were then hydroisomerized with a noble-metal impregnatedaluminosilicate of MRE structure type catalyst bound with alumina. Thereaction was carried out in a fixed bed reactor at 500 psig and 307° C.Cracked molecules were separated from the hydroisomerized C16 dimerusing an online stripper.

Example 2

The oligomerization and oligomer distillation were performed identicallyto Example 1. The dimers were then hydroisomerized with a noble-metalimpregnated aluminosilicate of MRE structure type catalyst bound withalumina. The reaction was carried out in a fix bed reactor at 500 psigand 313° C. Cracked molecules were separated from the hydroisomerizedC16 dimers using an online stripper.

Example 3

The oligomerization and oligomer distillation were performed identicallyto Example 1. The dimers were then hydroisomerized with a noble-metalimpregnated aluminosilicate of MRE structure type catalyst bound withalumina. The reaction was carried out in a fix bed reactor at 500 psigand 324° C. Cracked molecules were separated from the hydroisomerizedC16 dimers using an online stripper.

Example 4

The oligomerization and oligomer distillation were performed identicallyto Example 1. The dimers were then hydroisomerized with a noble-metalimpregnated aluminosilicate of MTT structure type catalyst bound withalumina. The reaction was carried out in a fix bed reactor at 500 psigand 316° C. Cracked molecules were separated from the hydroisomerizedC16 dimers using an online stripper.

Example 5

The oligomerization and oligomer distillation were performed identicallyto Example 1. The dimers were then hydroisomerized with a noble-metalimpregnated aluminosilicate of MTT structure type catalyst bound withalumina. The reaction was carried out in a fix bed reactor at 500 psigand 321° C. Cracked molecules were separated from the hydroisomerizedC16 dimers using an online stripper.

Example 6

The oligomerization and oligomer distillation were performed identicallyto Example 1. The dimers were then hydroisomerized with a noble-metalimpregnated aluminosilicate of MTT structure type catalyst bound withalumina. The reaction was carried out in a fix bed reactor at 500 psigand 332° C. Cracked molecules were separated from the hydroisomerizedC16 dimers using an online stripper.

Examples 7-12 (C≥42 Hydrocarbon Mixtures) Example 7

1-Hexadecene with less than 8% branched and internal olefins wasoligomerized under BF₃ with a co-catalyst composition of Butanol andButyl Acetate. The reaction was held at 20° C. during semi-continuousaddition of olefins and co-catalyst. The residence time was 90 minutes.The unreacted monomer was then distilled off, leaving behind less than0.1% monomer in the distillation bottoms. A subsequent distillation wasperformed to separate the dimer from the trimer and higher oligomers,the resulting dimer has less than 5% trimer.

The trimer and higher oligomers (trimer+) cut was then hydroisomerizedwith a noble-metal impregnated aluminosilicate of MRE structure typecatalyst bound with alumina. The reaction was carried out in a fixed bedreactor at 500 psig and 313° C. Cracked molecules were separated fromthe hydroisomerized C16 trimer+ using an online stripper.

Example 8

The oligomerization and subsequent distillations were performedidentically to Example 7. The trimer+ cut was then hydroisomerized witha noble-metal impregnated aluminosilicate of MRE structure type catalystbound with alumina. The reaction was carried out in a fix bed reactor at500 psig and 318° C. Cracked molecules were separated from thehydroisomerized C16 trimer+ using an online stripper.

Example 9

The oligomerization and subsequent distillations were performedidentically to Example 7. The trimer+ cut was then hydroisomerized witha noble-metal impregnated aluminosilicate of MRE structure type catalystbound with alumina. The reaction was carried out in a fix bed reactor at500 psig and 324° C. Cracked molecules were separated from thehydroisomerized C16 trimer+ using an online stripper.

Example 10

The oligomerization and subsequent distillations were performedidentically to Example 7. The trimer+ cut was then hydroisomerized witha noble-metal impregnated aluminosilicate of MTT structure type catalystbound with alumina. The reaction was carried out in a fix bed reactor at500 psig and 321° C. Cracked molecules were separated from thehydroisomerized C16 trimer+ using an online stripper.

Example 11

The oligomerization and subsequent distillations were performedidentically to Example 7. The trimer+ cut was then hydroisomerized witha noble-metal impregnated aluminosilicate of MTT structure type catalystbound with alumina. The reaction was carried out in a fix bed reactor at500 psig and 327° C. Cracked molecules were separated from thehydroisomerized C16 trimer+ using an online stripper.

Example 12

The oligomerization and subsequent distillations were performedidentically to Example 7. The trimer+ cut was then hydroisomerized witha noble-metal impregnated aluminosilicate of MTT structure type catalystbound with alumina. The reaction was carried out in a fix bed reactor at500 psig and 332° C. Cracked molecules were separated from thehydroisomerized C16 trimer+ using an online stripper.

Examples 13 and 14

Hexadecene with 75% alpha olefin and less than 8% branched and internalolefins was oligomerized under BF₃ with a co-catalyst composition ofButanol and Butyl Acetate. The reaction was held at 50° C. duringsemi-continuous addition of olefins and co-catalyst. The residence timewas 90 minutes. The unreacted monomer was then distilled off, leavingbehind less than 0.1% monomer distillation bottoms.

The dimer and higher oligomers were then hydroisomerized with anoble-metal impregnated aluminosilicate of MRE structure type catalystbound with alumina. The reaction was carried out in a fixed bed reactorat 350 psig and 300° C. Cracked molecules were separated from thehydroisomerized C16 dimer using an online stripper. A subsequentdistillation was performed to separate the dimer from the trimer+ withless than 5% trimer remained in the dimer cut. The distillation fractioncontaining the trimer+ was inspected and is reflected as Example 14.

Inspection results for the hydrocarbon mixtures obtained in examples1-14 are summarized in Table 3 below.

TABLE 3 Pour CCS Internal 5+ KV40, KV100, Noack, Point at −35° C.,Example BP/BI Alkyl Methyl cSt cSt VI wt % (° C.) cP No. 1 1.42 1.360.32 18.57 4.306 144 6.9 −27 1809 No. 2 1.19 1.67 0.50 18.67 4.297 142NM* −36 1384 No. 3 0.80 2.24 0.95 19.01 4.290 136 7.9 −51 1581 No. 41.28 1.46 0.42 18.76 4.324 143 7.0 −29 1480 No. 5 1.06 2.20 0.60 18.854.313 141 NM* −38 1430 No. 6 0.75 2.21 0.88 18.99 4.303 138 8.0 −48 1558No. 7 1.55 2.14 0.76 49.66 8.764 156 1.6 −19 26272 No. 8 1.30 2.57 1.1749.99 8.744 154 1.6 −24 11278 No. 9 0.94 3.56 1.37 50.76 8.730 151 1.7−34 10769 No. 10 1.41 2.75 1.14 48.93 8.642 156 1.9 −22 124967 No. 111.18 3.03 1.18 49.09 8.597 154 2.3 −28 18252 No. 12 0.95 2.94 1.29 49.448.533 150 2.2 −35 8589 No. 13 0.77 2.46 0.92 19.71 4.386 135  7.22 −461737 No. 14 1.14 3.15 1.14 27.45 5.567 146 2.0 −30 11105 *NM: notmeasured

In FIGS. 1 and 2, the relationship between BP/BI and internal alkylbranches per molecule, and 5+ methyl branches per molecule,respectively, is demonstrated for the hydrocarbon mixtures achieved bythe present process. FIG. 3 graphically depicts the relationship betweenNOACK volatility and CCS at −35° C. for the hydrocarbon productsobtained. The data in Table 3 confirms these unique relationships andcharacteristics.

Examples 15-21

Impact of boron triflouride oligomerization reaction temperatures on theoligomer structure and properties was studied. Higher reactiontemperature was found to increase the isomerization taking place duringthe oligomerization. To directly observe this effect by NMR, oligomerproducts were saturated and distilled into dimer and trimer+ fractions.The branching proximity for each dimer fraction example was measured.The results are shown below in Table 4 for samples 15 through 21.

TABLE 4 reaction temperature % alpha Branching Branching 5+ PP Example#(° C.) Olefin Proximity Index Methyl KV100 VI (° C.) Example 30 93 30.617.4 0.06 4.29 151 −15 #15 Example 50 93 28.7 19.5 0.08 4.33 148 −18 #16Example 80 93 26.5 20.5 0.27 4.35 143 −18 #17 Example 50 75 29.3 19.20.23 4.28 145 −18 #18 Example 50 60 31.6 18.69 0.1 4.33 144 −18 #19Example 30 60 30.5 19.1 0.12 4.31 147 −18 #20 Example 50 45 29.9 19.50.18 4.33 144 −21 #21

From the data it can be seen that as reaction temperature increases thelinearity of the fraction, as measured by Branching Proximity, isdecreased. This indicates an increase in the number of branches alongthe carbon backbone. The increased branching that results during hightemperature oligomerization does not provide the dimer fraction with therequired number of 5+ methyl branching per molecule needed to obtain adesirable pour point. The desired 5+ methyl branching is achievedthrough hydroisomerization of the oligomer product.

Increases in the methyl branching during oligomerization will result inhydroisomerized product with incorrect branching and non-ideal physicalproperties. A branching proximity of between 27-35 is required of thehydrogenated dimer prior to hydroisomerization.

Example 15

Hexadecene with 93% alpha olefin and less than 8% branched and internalolefins was oligomerized under BF₃ with a co-catalyst composition ofButanol and Butyl Acetate. The reaction was held at 30° C. duringsemi-continuous addition of olefins and co-catalyst. The residence timewas 90 minutes. The unreacted monomer was then distilled off, leavingbehind less than 0.1% monomer distillation bottoms. A subsequentdistillation was performed to separate the dimer from the trimer+ withless than 5% trimer remained in the dimer cut. The dimer cut wassubsequently hydrogenated without isomerization.

Example 16

Hexadecene with 93% alpha olefin and less than 8% branched and internalolefins was oligomerized under BF₃ with a co-catalyst composition ofButanol and Butyl Acetate. The reaction was held at 50° C. duringsemi-continuous addition of olefins and co-catalyst. The residence timewas 90 minutes. The unreacted monomer was then distilled off, leavingbehind less than 0.1% monomer distillation bottoms. A subsequentdistillation was performed to separate the dimer from the trimer+ withless than 5% trimer remained in the dimer cut. The dimer cut wassubsequently hydrogenated without isomerization.

Example 17

Hexadecene with 93% alpha olefin and less than 8% branched and internalolefins was oligomerized under BF₃ with a co-catalyst composition ofButanol and Butyl Acetate. The reaction was held at 80° C. duringsemi-continuous addition of olefins and co-catalyst. The residence timewas 90 minutes. The unreacted monomer was then distilled off, leavingbehind less than 0.1% monomer distillation bottoms. A subsequentdistillation was performed to separate the dimer from the trimer+ withless than 5% trimer remained in the dimer cut. The dimer cut wassubsequently hydrogenated without isomerization.

Example 18

Hexadecene with 75% alpha olefin and less than 1% branched and internalolefins was oligomerized under BF₃ with a co-catalyst composition ofButanol and Butyl Acetate. The reaction was held at 50° C. duringsemi-continuous addition of olefins and co-catalyst. The residence timewas 120 minutes. The unreacted monomer was then distilled off, leavingbehind less than 0.1% monomer distillation bottoms. A subsequentdistillation was performed to separate the dimer from the trimer+ withless than 5% trimer remained in the dimer cut. The dimer cut wassubsequently hydrogenated without isomerization.

Example 19

Hexadecene with 60% alpha olefin and less than 1% branched and internalolefins was oligomerized under BF₃ with a co-catalyst composition ofButanol and Butyl Acetate. The reaction was held at 50° C. duringsemi-continuous addition of olefins and co-catalyst. The residence timewas 120 minutes. The unreacted monomer was then distilled off, leavingbehind less than 0.1% monomer distillation bottoms. A subsequentdistillation was performed to separate the dimer from the trimer+ withless than 5% trimer remained in the dimer cut. The dimer cut wassubsequently hydrogenated without isomerization.

Example 20

Hexadecene with 60% alpha olefin and less than 1% branched and internalolefins was oligomerized under BF₃ with a co-catalyst composition ofButanol and Butyl Acetate. The reaction was held at 30° C. duringsemi-continuous addition of olefins and co-catalyst. The residence timewas 120 minutes. The unreacted monomer was then distilled off, leavingbehind less than 0.1% monomer distillation bottoms. A subsequentdistillation was performed to separate the dimer from the trimer+ withless than 5% trimer remained in the dimer cut. The dimer cut wassubsequently hydrogenated without isomerization.

Example 21

Hexadecene with 45% alpha olefin and less than 1% branched and internalolefins was oligomerized under BF₃ with a co-catalyst composition ofButanol and Butyl Acetate. The reaction was held at 50° C. duringsemi-continuous addition of olefins and co-catalyst. The residence timewas 120 minutes. The unreacted monomer was then distilled off, leavingbehind less than 0.1% monomer distillation bottoms. A subsequentdistillation was performed to separate the dimer from the trimer+ withless than 5% trimer remained in the dimer cut. The dimer cut wassubsequently hydrogenated without isomerization.

That which is claimed is:
 1. A process for preparing a base stock,comprising: (i) providing an olefinic feedstock comprising C14 to C20olefins which comprises less than 40 wt % branched olefins and greaterthan 40 wt % alpha olefins; (ii) oligomerizing the olefinic feedstockusing a boron trifluoride catalyst at a reaction temperature in a rangeof from 20-60° C., while controlling the reaction conditions to obtainan intermediate having a dimers fraction such that the dimers fractionof the intermediate when saturated without hydroisomerization results ina saturated dimer with a branching proximity of 27-35; and (iii)hydroisomerizing at least a portion of the intermediate obtained fromstep (ii) using a metal impregnated one-dimensional, 10-member ringzeolite catalyst to achieve a C28+ product with BP/BI≥−0.6037*(Internalalkyl branching per molecule)+2.0 and on average 0.3 to 1.5 methylbranches on the fifth or greater position per molecule.
 2. The processof claim 1, wherein the olefinic feedstock comprises greater than 50 wt% alpha olefins.
 3. The process of claim 2, wherein the olefinicfeedstock comprises less than 8 wt % branched olefins.
 4. The process ofclaim 1, wherein the olefinic feedstock comprises greater than 70 wt %alpha olefins.
 5. The process of claim 1, wherein the boron trifluoridecatalyst used in the oligomerizing of (ii) further comprises an alcoholpromoter, and an ester promoter.
 6. The process of claim 1, wherein theresidence time for the oligomerization reaction ranges from 60-180minutes.
 7. The process of claim 2, further comprising recovering theintermediate, removing unreacted monomer from the intermediate, andrecovering a resulting intermediate prior to step (iii).
 8. The processof claim 7, wherein the unreacted monomer removed is recycled to theolefinic feedstock of step (i).
 9. The process of claim 7, furthercomprising hydrogenating the resulting intermediate to create ahydrogenated intermediate, the hydrogenated intermediate is thensubjected to the hydroisomerization of step (iii); and recovering aproduct from the hydroisomerization and separating product from thehydroisomerization into a fraction comprising greater than 95 wt %dimers having a maximum carbon number of 40, and a fraction comprisinggreater than 95 wt % trimers and higher oligomers having a minimumcarbon number of
 42. 10. The process of claim 7, wherein the resultingintermediate is separated into a fraction comprising greater than 95 wt% dimers having a maximum carbon number of 40, and a fraction comprisinggreater than 95% trimers and higher oligomers having a minimum carbonnumber of
 42. 11. The process of claim 10, further comprisinghydroisomerizing each of the fractions separately.
 12. The process ofclaim 7, wherein the resulting intermediate is further hydrogenated tocreate a hydrogenated intermediate, with the hydrogenated intermediatecomprising dimers having a maximum carbon number of 40 and a branchingproximity from 28-32.
 13. The process of claim 2, wherein thehydroisomerizing is conducted under a pressure of 100-800 psig; atemperature in a range of from 290-350° C., and a hydrogen flow rate of500-3500 scf/bbl.
 14. A process for preparing a base stock, comprising:(i) providing an olefinic feedstock comprising less than 8 wt % branchedmonomeric olefins and greater than 50 wt % monomeric alpha olefins, withthe monomeric olefins having a carbon number in the range of fromC14-C20; (ii) conducting an oligomerization reaction with the olefinicfeedstock of (i) at a temperature in the range of from 20 to 60° C.,over a BuOH and BuAc co-catalyst, with a reaction residence time of from60-180 minutes, in a semi-batch or continuous stirred tank reactor,while controlling the reaction conditions to obtain an intermediate witha dimers fraction such that the dimers fraction of the intermediate whensaturated without hydroisomerization results in a saturated dimer with abranching proximity of 27-35; (iii) recovering the intermediate from theoligomerization reaction in step (ii), removing unreacted monomer bydistillation, and recovering a resulting intermediate from thedistillation; (iv) hydrogenating the resulting intermediate recoveredfrom the distillation in (iii); (v) recovering a hydrogenation productfrom the hydrogenation in (iv) and hydroisomerizing the hydrogenationproduct over a metal impregnated, one-dimensional zeolite with a10-member ring at a pressure in the range of from 100-800 psig; atemperature in the range of from 290-350° C.; and at a hydrogen flowrate of 500-3500 scf/bbl to produce a hydroisomerized product; (vi)recycling the unreacted monomer removed in (iii) to the olefinicfeedstock in (i); and (vii) separating a dimers fraction and a trimersand higher oligomers fraction from the hydroisomerized product of step(v), with the dimers fraction comprising greater than or equal to 95 wt% dimers having a maximum carbon number of
 40. 15. A process forpreparing a base stock, comprising: (i) providing an olefinic feedstockcomprising less than 8 wt % branched monomeric olefins and greater than50 wt % monomeric alpha olefins, with the monomeric olefins having acarbon number in the range of from C14-C20; (ii) conducting anoligomerization reaction with the olefinic feedstock of (i) at atemperature in the range of from 20 to 60° C., over a BuOH and BuAcco-catalyst, with a reaction residence time of from 60-180 minutes, in asemi-batch or continuous stirred tank reactor, while controlling thereaction conditions to obtain an intermediate with a dimers fractionsuch that the dimers fraction of the intermediate when saturated withouthydroisomerization results in a saturated dimer with a branchingproximity of 27-35; (iii) recovering the intermediate from theoligomerization reaction in step (ii), removing unreacted monomer bydistillation; (iv) recovering a bottoms product from the distillation in(iii) and hydroisomerizing the bottoms product over a metal impregnated,one-dimensional zeolite with a 10-member ring at a pressure in the rangeof from 100-800 psig; a temperature in the range of from 290-350° C.;and at a hydrogen flow rate of 500-3500 scf/bbl; (v) recycling theunreacted monomer removed in (iii) to the olefinic feedstock in (i); and(vi) recovering a hydroisomerization product from the hydroisomerizationin (iv) and separating the hydroisomerization product into a dimerfraction comprising dimers having a carbon number in the range of fromC28-C40, and a trimer and higher oligomers fraction-comprising compoundshaving a carbon number of 42 and higher.
 16. A process for preparing abase stock, comprising: (i) providing an olefinic feedstock comprisingless than 8 wt % branched monomeric olefins and greater than 50 wt %monomeric alpha olefins, with the monomeric olefins having a carbonnumber in the range of from C14-C20; (ii) conducting an oligomerizationreaction with the olefinic feedstock of (i) at a temperature in therange of from 20 to 60° C., over a BuOH and BuAc co-catalyst, with areaction residence time of from 60-180 minutes, in a semi-batch orcontinuous stirred tank reactor, while controlling the reactionconditions to obtain an intermediate with a dimers/fraction such thatthe dimers fraction of the intermediate when saturated withouthydroisomerization results in a saturated dimer with a branchingproximity of 27-35; (iii) recovering the intermediate from theoligomerization reaction in step (ii), removing unreacted monomer bydistillation, and recovering a bottoms distillation product; (iv)separating a dimers fraction and a trimers and higher oligomers fractionfrom the bottoms distillation product of (iii), with the dimers fractioncomprising greater than or equal to 95% compounds having a maximumcarbon number of 40, and with the trimers and higher oligomers fractioncomprising compounds having a carbon number of 42 and greater; and (v)hydroisomerizing each fraction in (iv) separately over a metalimpregnated, one-dimensional zeolite with a 10-member ring at a pressurein the range of from 100-800 psig; a temperature in the range of from290-350° C.; and at a hydrogen flow rate of 500-3500 scf/bbl.
 17. Theprocess of claim 1, wherein the metal impregnated 10 member ring zeolitecatalyst is impregnated with Pt, Pd, or a mixture thereof.